November 14, 2013

Scientists writing in the Journal of Climate claim the Amazon rain forest may be more resilient in its ability to cope with dry conditions than previously believed. Researchers from the University of Exeter and Colorado State University used a computer model to demonstrate that the Amazon rainforest may be able to withstand periods of drought better than what previous climate models had predicted.

During the study, researchers removed unrealistic water stress from their model and found the moisture that is recycled by the forest is sufficient to reduce the intensity of drought conditions.

"This study suggests that forests are not only more able to withstand droughts than we had previously thought, but it is the response of the forest itself that can reduce the intensity or length of the drought,” said Dr Anna Harper from the University of Exeter. "Moisture recycling works best in large areas of undisturbed forest so it is essential that measures to protect the Amazon rain forest are in place to ensure that that this natural process can be maintained in what may be a drier climate in the future."

Moisture recycling includes soil moisture to evaporated water vapor that can cycle back to create rain. This process depends on water both evaporating from the ground and also moving through plants from the roots to the leaves. Moisture recycling is an important source of rainfall over the Amazon forest, with scientists estimating about one-third of the annual rainfall in the southern Amazon forest originates from moisture recycling.

This process relies upon the ability of plants to access soil moisture. During a severe drought, trees can reach a limit in their ability to access and use soil moisture. Many ecosystem models show plants reach this limit too soon, increasing the water stress that plants are experience during the dry season. However, moisture recycling can increase during the dry season, resulting in increased atmosphere moisture and even rain, which makes trees more resistant to drought.

With the changing climate, scientists believe drought is going to become an increasing problem in the coming years and forest conservation can help mitigate the consequences. Large areas of undisturbed forest are more able to maintain moisture recycling during dry periods and are more able to recycle rainfall.

Moisture recycling does not make the forest immune to drought, but it can make the impacts of drought less severe than previously thought.